The device of the present invention relates to wood furnaces. Specifically, it relates to warning devices that may be attached to a wood furnace that would activate an alarm notifying the owner that the furnace is overheating.
The use of burning wood to heat a home is old and well known. For example, one of the many achievements for which Ben Franklin is noted was the invention of a superior type of wood burning stove. As other sources of energy, like gas and electric, became available the use of wood burning furnaces decreased. Interest in burning wood to heat a home was renewed as a result of the movement towards energy conservation during the 1970's. A major problem with wood burning furnaces is that of temperature regulation. Without proper regulation of the temperature a wood burning furnace may overheat and present a fire hazard. By means of a unique and simple design the present invention provides the owner of a wood burning furnace the ability to prevent his furnace from overheating.
Although many temperature sensing/warning devices are known, none are known to the inventor that work in the same manner as the inventor's device. For example, U.S. Pat. No. 2,982,949 (Pivetz) discloses a box containing an alarm bell and arm light, however, the invention is designed to be portable rather than secured to a wood furnace and the heat sensitive switch used is of an older design. Furthermore, the invention requires a 110 volt cord to bring in house current, an electric light bulb, a flasher, a thermostatic switch which specifically requires a bi-metallic blade, various insulating blocks which the present invention does not require, and a great deal of other specific structure. Also, the box used in the Pivetz patent is made of plastic rather than metal and does not serve to limit the heat the alarm circuit is exposed to by transferring the heat away from the alarm circuit through the metal of the box. U.S. Pat. No. 2,807,013 (Prough), relates to a heat sensing unit fastened to the flue of a furnace. A warning bell and a transformer are located elsewhere so the entire device is not in a box attached to the furnace. The Prough patent provides that if the flue fails the hot gases are diverted directly into the housing 15 of the arlarm switch. The present invention does not operate in that manner. U.S. Pat. No. 2,493,548 (Proctor) relates to a boiler alarm which responds to the level of liquid and to both high and low pressure in the boiler. The invention in no way relates to wood burning furnaces. U.S. Pat. No. 2,446,794 (Thornton) shows a portable fire alarm which includes a metal box having batteries, a heat sensitive switch, and a buzzer. However, unlike the present invention Thorton is designed to be portable rather permanently fixed to the wood furnace and the heat sensor is internally located. Furthermore, the heat sensor or switch contained within the Thornton invention has its contacts exposed; this may cause the switch to get dirty and fail. The contacts of the heat sensor in the present invention are enclosed. So any dirt that could get into the box through the vents will not cause the contacts to get dirty and fail. U.S. Pat. No. 3,959,787 (Messmann et.al.) relates to a self-enclosed alarm which is intended to respond to a high temperature in a refrigerated container. The sensing unit and the alarm are not contained within the same box. U.S. Pat. No. 3,932,849 (Welch) discloses a heat sensor having a probe which is inserted in food that is to be cooked and notifies the user when the desired temperature has been reached. U.S. Pat. No. 3,827,039 (Agnese) discloses a portable alarm system that is designed to function as both a fire and a burglar alarm. The fire alarm is tripped when a spring loaded fusible element must be destroyed upon attainment of a predetermined temperature. This causes the alarm to trip and the inventor suggests that it may also turn on subsidiary systems such as a room sprinkler. Unlike the present invention the heat sensing element of the Agnese patent is destroyed upon the attainment of a specific temperature where in the present invention the heat sensing element is designed to withstand the heat of the predetermined temperature time after time.